The Sun loses 4 million tonnes of mass every second

The Sun converts approximately 600 million tonnes of hydrogen into helium every second through nuclear fusion. In the process, 4 million tonnes of that mass are converted directly into energy via E=mc², which powers everything from sunlight to solar wind. Over the Sun's 4.6-billion-year lifetime, it has converted roughly 100 Earth-masses of material into pure energy. Despite this, the Sun has lost only about 0.03% of its total mass — it contains enough hydrogen fuel to continue burning for another 5 billion years before expanding into a red giant.

Source: Carroll & Ostlie, Introduction to Modern Astrophysics (2017)